Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Summary of Investments in Community Development and Tax-advantaged VIEs (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Investment carrying amount	$ 668,039	$ 674,805
Unfunded capital and other commitments	614,461	623,573
Variable Interest Entity Not Primary Beneficiary [Member] | Community Development And Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Investment carrying amount	6,488	5,452
Unfunded capital and other commitments	3,186	2,416
Maximum exposure to loss	$ 10,058	$ 9,761